/*
 * Copyright 2002-2006 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.context;

import javax.servlet.ServletContext;

import org.springframework.context.ApplicationContext;

/**
 * 为一个Web应用提供配置信息的接口。当应用在运行的时候，是只读的，除非接口的实现类支持reloaded。<br/>
 * Interface to provide configuration for a web application. This is read-only
 * while the application is running, but may be reloaded if the implementation
 * supports this.
 * 
 * <p>
 * This interface adds a getServletContext method to the generic
 * ApplicationContext interface, and defines a well-known application attribute
 * name that the root context must be bound to in the bootstrap process.
 * 
 * <p>
 * Like generic application contexts, web application contexts are hierarchical.
 * There is a single root context per application, while each servlet in the
 * application (including a dispatcher servlet in the MVC framework) has its own
 * child context.
 * 
 * <p>
 * In addition to standard application context lifecycle capabilities,
 * WebApplicationContext implementations need to detect ServletContextAware
 * beans and invoke the setServletContext method accordingly.
 * 
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since January 19, 2001
 * @see ServletContextAware#setServletContext
 */
public interface WebApplicationContext extends ApplicationContext {

	/**
	 * #Comment#:在上下文启动之后，WebApplicationContext即以此为键放置在ServletContext的属性列表中，
	 * 可以直接通过servletContext.getAttribute的方式获取WebApplicationContext。
	 * <p>
	 * 成功启动后，Context绑定到root WebApplicationContext的属性名称。<br/>
	 * Context attribute to bind root WebApplicationContext to on successful
	 * startup.
	 * <p>
	 * Note: If the startup of the root context fails, this attribute can
	 * contain an exception or error as value. Use WebApplicationContextUtils
	 * for convenient lookup of the root WebApplicationContext.
	 * 
	 * @see org.springframework.web.context.support.WebApplicationContextUtils#getWebApplicationContext
	 * @see org.springframework.web.context.support.WebApplicationContextUtils#getRequiredWebApplicationContext
	 */
	String ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE = WebApplicationContext.class
			.getName() + ".ROOT";

	/**
	 * Scope identifier for request scope: "request". Supported in addition to
	 * the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_REQUEST = "request";

	/**
	 * Scope identifier for session scope: "session". Supported in addition to
	 * the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_SESSION = "session";

	/**
	 * Scope identifier for global session scope: "globalSession". Supported in
	 * addition to the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_GLOBAL_SESSION = "globalSession";

	/**
	 * Return the standard Servlet API ServletContext for this application.
	 */
	ServletContext getServletContext();

}
